Differential output mode for a multi-mode power converter

ABSTRACT

A switching power stage for producing an output voltage to a load may include a power converter and a controller. The power converter may include a power inductor and plurality of switches arranged to sequentially operate in a plurality of switch configurations. The controller may be configured to, based on a measured parameter associated with the switching power stage, select a selected operational mode of the power converter from a plurality of operational modes, and sequentially apply switch configurations from the plurality of switch configurations to selectively activate or deactivate each of the plurality of switches in order to transfer electrical energy from an input source of the power converter to the load in accordance with the selected operational mode. 
     A switching power stage for producing an output voltage to a load may include a power converter and a controller. The power converter may include a power inductor and plurality of switches arranged to sequentially operate in a plurality of switch configurations. The controller may be configured to, based at least on an input signal to the switching power stage, determine the differential output voltage to be driven at the load, and based on the differential output voltage to be driven at the load, apply a switch configuration from the plurality of switch configurations to selectively activate or deactivate each of the plurality of switches in order to generate the differential output voltage. 
     A method may include sequentially applying a plurality of switch configurations in a power converter to selectively activate or deactivate each of the plurality of switches in order operate the power converter as a differential output buck converter, such that: during a charging phase of the power converter, the power inductor is coupled between (i) one of a first terminal of a power source and a second terminal of the power source and (ii) one of a first terminal of the output load and a second terminal of the output load; during a transfer phase of the power converter, at least one of the plurality of switches is activated in order to couple the power inductor between the first terminal of the output load and a second terminal of the output load; and the output voltage is a differential voltage between the first and second terminal of the output load.

RELATED APPLICATIONS

The present disclosure claims priority to U.S. Provisional PatentApplication Ser. No. 61/935,725, filed Feb. 4, 2014, U.S. ProvisionalPatent Application Ser. No. 61/990,363, filed May 8, 2014, and U.S.Provisional Patent Application Ser. No. 62/072,059, filed Oct. 29, 2014,each of which is incorporated by reference herein in its entirety.

FIELD OF DISCLOSURE

The present disclosure relates in general to circuits for audio devices,including without limitation personal audio devices such as wirelesstelephones and media players, and more specifically, to a switch modeamplifier for driving an audio transducer of an audio device.

BACKGROUND

Personal audio devices, including wireless telephones, such asmobile/cellular telephones, cordless telephones, mp3 players, and otherconsumer audio devices, are in widespread use. Such personal audiodevices may include circuitry for driving a pair of headphones or one ormore speakers. Such circuitry often includes a speaker driver includinga power amplifier for driving an audio output signal to headphones orspeakers.

One existing approach to driving an audio output signal is to employ aspeaker driver, such as speaker driver 100 depicted in FIG. 1. Speakerdriver 100 may include an envelope-tracking boost converter 102 (e.g., aClass H amplifier) followed by a full-bridge output stage 104 (e.g., aClass D amplifier) which effectively operates as another converterstage. Boost converter 102 may include a power inductor 104, switches106, 108, and a capacitor 110 arranged as shown. Full-bridge outputstage 104 may include switches 112, 114, 116, and 118, inductors 120 and124, and capacitors 122 and 126 as shown.

Speaker drivers such as speaker driver 100 suffer from numerousdisadvantages. One disadvantage is that due to switching in output stage104, such a speaker driver 100 may give rise to large amounts ofradiated electromagnetic radiation, which may cause interference withother electromagnetic signals. Such radiated electromagneticinterference may be mitigated by LC filters formed using inductor 120and capacitor 122 and inductor 124 and capacitor 126. However, such LCfilters are often quite large in size, and coupling capacitors 122 and124 to the terminals of the output transducer may have a negative impacton the power efficiency of speaker driver 100.

In addition, such architectures often do not handle large impulsivesignals. To reduce power consumption, a power supply voltage V_(SUPPLY)may be varied in accordance with the output signal, such that V_(SUPPLY)may operate at lower voltage levels for lower output signal magnitudes.Thus, if a signal quickly increases, adequate time may not be present toincrease voltage V_(SUPPLY), thus leading to signal clipping unless adelay is placed in the signal path. However, adding a delay to a signalpath may cause incompatibility with other types of audio circuits, suchas adaptive noise cancellation circuits.

SUMMARY

In accordance with the teachings of the present disclosure, one or moredisadvantages and problems associated with existing approaches todriving an audio output signal to an audio transducer may be reduced oreliminated.

In accordance with embodiments of the present disclosure, a switchingpower stage for producing an output voltage to a load may include apower converter and a controller. The power converter may include apower inductor, a plurality of switches, an output, and at least onecapacitor. The plurality of switches may be arranged to sequentiallyoperate in a plurality of switch configuration. The output may be forproducing the output voltage comprising a first output terminal and asecond output terminal, wherein a first switch of the plurality ofswitches is coupled between the power inductor and the first outputterminal and a second switch of the plurality of switches is coupledbetween the power inductor and the second output terminal. The capacitormay be coupled to one of the first output terminal and the second outputterminal. The controller may be configured to, based on a measuredparameter associated with the switching power stage, select a selectedoperational mode of the power converter from a plurality of operationalmodes, and sequentially apply switch configurations from the pluralityof switch configurations to selectively activate or deactivate each ofthe plurality of switches in order to transfer electrical energy from aninput source of the power converter to the load in accordance with theselected operational mode.

In accordance with these and other embodiments of the presentdisclosure, a method for producing an output voltage to a load mayinclude, based on a measured parameter associated with a switching powerstage having a power converter comprising a power inductor, a pluralityof switches arranged to sequentially operate in a plurality of switchconfigurations, an output for producing the output voltage comprising afirst output terminal and a second output terminal, wherein a firstswitch of the plurality of switches is coupled between the powerinductor and the first output terminal and a second switch of theplurality of switches is coupled between the power inductor and thesecond output terminal, at least one of: a capacitor coupled to thefirst output terminal and a capacitor coupled to the second outputterminal, selecting a selected operational mode of the power converterfrom a plurality of operational modes. The method may also includesequentially applying a switch configurations from the plurality ofswitch configurations to selectively activate or deactivate each of theplurality of switches in order to transfer electrical energy from aninput source of the power converter to the load in accordance with theselected operational mode.

In accordance with these and other embodiments of the presentdisclosure, a switching power stage for producing an output voltage to aload may include a power converter and a controller. The power convertermay include a power inductor and plurality of switches arranged tosequentially operate in a plurality of switch configurations inaccordance with a selected operational mode of the power converter, theselected operational selected from a plurality of operational modes. Theplurality of operational modes may include a buck configuration whereinthe plurality of switches are selectively enabled and disabled such thatthe power converter operates as a buck converter when in the buckconfiguration and a boost configuration wherein the plurality ofswitches are selectively enabled and disabled such that the powerconverter operates as a boost converter when in the boost configuration.The controller may be configured to sequentially apply switchconfigurations from the plurality of switch configurations toselectively activate or deactivate each of the plurality of switches inorder to transfer electrical energy from an input source of the powerconverter to the load in accordance with the selected operational mode.

In accordance with these and other embodiments of the presentdisclosure, a method for producing an output voltage to a load mayinclude sequentially operating a power converter comprising a powerinductor and plurality of switches in a plurality of switchconfigurations in accordance with a selected operational mode of thepower converter, the selected operational selected from a plurality ofoperational modes. The selected operation modes may include a buckconfiguration wherein the plurality of switches are selectively enabledand disabled such that the power converter operates as a buck converterwhen in the buck configuration and a boost configuration wherein theplurality of switches are selectively enabled and disabled such that thepower converter operates as a boost converter when in the boostconfiguration. The method may also include sequentially applying switchconfigurations from the plurality of switch configurations toselectively activate or deactivate each of the plurality of switches inorder to transfer electrical energy from an input source of the powerconverter to the load in accordance with the selected operational mode.

In accordance with these and other embodiments of the presentdisclosure, a switching power stage for producing an output voltage to aload may include a power converter and a controller. The power convertermay include a power inductor and plurality of switches arranged tosequentially operate in a plurality of switch configurations. Thecontroller may be configured to select a selected operational mode ofthe power converter from a plurality of operational modes, the pluralityof operational modes comprising at least: (a) a first operational modein which a first terminal of the load is at a voltage potential lowerthan that of a first terminal of a power source to the power converterand a second terminal of the load is at a voltage potential higher thanthat of a second terminal of the power source; and (b) a secondoperational mode in which one of the first terminal of the load and thesecond terminal of the load is coupled with a switch of the plurality ofswitches to one of the first terminal of the power source and the secondterminal of the power source. The controller may also be configured tosequentially apply switch configurations from the plurality of switchconfigurations to selectively activate or deactivate each of theplurality of switches in order to transfer electrical energy from aninput source of the power converter to the load in accordance with theselected operational mode.

In accordance with these and other embodiments of the presentdisclosure, a switching power stage for producing an output voltage to aload may include a power converter and a controller. The power convertermay include a power inductor and plurality of switches arranged tosequentially operate in a plurality of switch configurations. Thecontroller may be configured to, based at least on an input signal tothe switching power stage, determine the differential output voltage tobe driven at the load, and based on the differential output voltage tobe driven at the load, apply a switch configuration from the pluralityof switch configurations to selectively activate or deactivate each ofthe plurality of switches in order to generate the differential outputvoltage.

In accordance with these and other embodiments of the presentdisclosure, a method for producing an output voltage to a load mayinclude selecting a selected operational mode for a power convertercomprising a power inductor and plurality of switches arranged tosequentially operate in a plurality of switch configurations. Theplurality of operational modes may include at least a first operationalmode in which a first terminal of the load is at a voltage potentiallower than that of a first terminal of a power source to the powerconverter and a second terminal of the load is at a voltage potentialhigher than that of a second terminal of the power source and a secondoperational mode in which one of the first terminal of the load and thesecond terminal of the load is coupled with a switch of the plurality ofswitches to one of the first terminal of the power source and the secondterminal of the power source. The method may also include sequentiallyapplying switch configurations from the plurality of switchconfigurations to selectively activate or deactivate each of theplurality of switches in order to transfer electrical energy from aninput source of the power converter to the load in accordance with theselected operational mode.

In accordance with these and other embodiments of the presentdisclosure, a method for producing an output voltage to a load mayinclude, based at least on an input signal to a switching power stagefor producing a differential output voltage to a load, wherein theswitching power stage comprises a power inductor and plurality ofswitches arranged to sequentially operate in a plurality of switchconfigurations, determining the differential output voltage to be drivenat the load. The method may also include, based on the differentialoutput voltage to be driven at the load, applying a switch configurationfrom the plurality of switch configurations to selectively activate ordeactivate each of the plurality of switches in order to generate thedifferential output voltage.

In accordance with these and other embodiments of the presentdisclosure, a switching power stage for producing an output voltage to aload may include a power converter and a controller. The power convertermay include a power inductor and plurality of switches arranged tosequentially operate in a plurality of switch configurations. Thecontroller may be configured to sequentially apply the plurality ofswitch configurations to selectively activate or deactivate each of theplurality of switches in order to operate the power converter as adifferential output buck converter, such that: (a) during a chargingphase of the power converter, the power inductor is coupled between (i)one of a first terminal of a power source and a second terminal of thepower source and (ii) one of a first terminal of the output load and asecond terminal of the output load; (b) during a transfer phase of thepower converter, at least one of the plurality of switches is activatedin order to couple the power inductor between the first terminal of theoutput load and a second terminal of the output load; and (c) the outputvoltage comprises a differential voltage between the first terminal andthe second terminal.

In accordance with these and other embodiments of the presentdisclosure, a method for producing an output voltage to a load mayinclude, in a power converter comprising a power inductor and pluralityof switches arranged to sequentially operate in the plurality of switchconfigurations, sequentially applying a plurality of switchconfigurations to selectively activate or deactivate each of theplurality of switches in order to operate the power converter as adifferential output buck converter, such that: (a) during a chargingphase of the power converter, the power inductor is coupled between (i)one of a first terminal of a power source and a second terminal of thepower source and (ii) one of a first terminal of the output load and asecond terminal of the output load; (b) during a transfer phase of thepower converter, at least one of the plurality of switches is activatedin order to couple the power inductor between the first terminal of theoutput load and a second terminal of the output load; and (c) the outputvoltage comprises a differential voltage between the first terminal andthe second terminal.

Technical advantages of the present disclosure may be readily apparentto one skilled in the art from the figures, description and claimsincluded herein. The objects and advantages of the embodiments will berealized and achieved at least by the elements, features, andcombinations particularly pointed out in the claims.

It is to be understood that both the foregoing general description andthe following detailed description are examples and explanatory and arenot restrictive of the claims set forth in this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present embodiments and advantagesthereof may be acquired by referring to the following description takenin conjunction with the accompanying drawings, in which like referencenumbers indicate like features, and wherein:

FIG. 1 illustrates an example speaker driver, as is known in therelevant art.

FIG. 2 illustrates an example personal audio device, in accordance withembodiments of the present disclosure;

FIG. 3 illustrates a block diagram of selected components of an exampleaudio integrated circuit of a personal audio device, in accordance withembodiments of the present disclosure;

FIG. 4 illustrates a block and circuit diagram of selected components ofan example switched mode amplifier, in accordance with embodiments ofthe present disclosure;

FIG. 5 illustrates a circuit diagram of selected components of anexample power converter, in accordance with embodiments of the presentdisclosure;

FIG. 6 illustrates a table setting forth switch configurations of thepower converter of FIG. 5 when operating in boost mode, in accordancewith embodiments of the present disclosure;

FIG. 7 illustrates an equivalent circuit diagram of selected componentsof the power converter of FIG. 5 operating in a charging phase of aboost mode, in accordance with embodiments of the present disclosure;

FIG. 8 illustrates an equivalent circuit diagram of selected componentsof the power converter of FIG. 5 operating in a discharge phase of aboost mode, in accordance with embodiments of the present disclosure;

FIG. 9 illustrates a table setting forth switch configurations of thepower converter of FIG. 5 when operating in buck mode, in accordancewith embodiments of the present disclosure;

FIG. 10 illustrates an equivalent circuit diagram of selected componentsof the power converter of FIG. 5 operating in a charging phase of a buckmode, in accordance with embodiments of the present disclosure;

FIG. 11 illustrates an equivalent circuit diagram of selected componentsof the power converter of FIG. 5 operating in a discharge phase of abuck mode, in accordance with embodiments of the present disclosure;

FIG. 12 illustrates a circuit diagram of selected components of anotherexample power converter, in accordance with embodiments of the presentdisclosure;

FIG. 13 illustrates a table setting forth switch configurations of thepower converter of FIG. 12 when operating in a single-ended boost mode,in accordance with embodiments of the present disclosure;

FIG. 14 illustrates an equivalent circuit diagram of selected componentsof the power converter of FIG. 12 operating in a charging phase of asingle-ended boost mode, in accordance with embodiments of the presentdisclosure;

FIG. 15 illustrates an equivalent circuit diagram of selected componentsof the power converter of FIG. 12 operating in a discharge phase of asingle-ended boost mode, in accordance with embodiments of the presentdisclosure;

FIG. 16 illustrates a table setting forth switch configurations of thepower converter of FIG. 12 when operating in a differential-outputbuck-boost mode, in accordance with embodiments of the presentdisclosure;

FIG. 17 illustrates an equivalent circuit diagram of selected componentsof the power converter of FIG. 12 operating in a charging phase of adifferential-output buck-boost mode, in accordance with embodiments ofthe present disclosure;

FIG. 18 illustrates an equivalent circuit diagram of selected componentsof the power converter of FIG. 12 operating in a discharge phase of adifferential-output buck-boost mode, in accordance with embodiments ofthe present disclosure;

FIG. 19 illustrates a table setting forth switch configurations of thepower converter of FIG. 12 when operating in a differential-output buckmode, in accordance with embodiments of the present disclosure;

FIG. 20 illustrates an equivalent circuit diagram of selected componentsof the power converter of FIG. 12 operating in a charging phase of adifferential-output buck mode, in accordance with embodiments of thepresent disclosure;

FIG. 21 illustrates an equivalent circuit diagram of selected componentsof the power converter of FIG. 12 operating in another charging phase ofa differential-output buck mode, in accordance with embodiments of thepresent disclosure;

FIG. 22 illustrates an equivalent circuit diagram of selected componentsof the power converter of FIG. 12 operating in a discharge phase of adifferential-output buck mode, in accordance with embodiments of thepresent disclosure;

FIG. 23 illustrates a circuit diagram of selected components of anotherexample power converter, in accordance with embodiments of the presentdisclosure;

FIG. 24 illustrates a graph of an example output voltage having asinusoidal waveform, the graph indicating example ranges for operationin the various operational modes of the power converter of FIG. 12, inaccordance with embodiments of the present disclosure;

FIG. 25 illustrates a block diagram of selected components of an examplemodulator, in accordance with embodiments of the present disclosure;

FIG. 26 illustrates a block diagram of selected components of anotherexample modulator, in accordance with embodiments of the presentdisclosure; and

FIG. 27 illustrates a block diagram of selected components of a powerconverter control, in accordance with embodiments of the presentdisclosure.

DETAILED DESCRIPTION

FIG. 2 illustrates an example personal audio device 1, in accordancewith embodiments of the present disclosure. FIG. 2 depicts personalaudio device 1 coupled to a headset 3 in the form of a pair of earbudspeakers 8A and 8B. Headset 3 depicted in FIG. 2 is merely an example,and it is understood that personal audio device 1 may be used inconnection with a variety of audio transducers, including withoutlimitation, headphones, earbuds, in-ear earphones, and externalspeakers. A plug 4 may provide for connection of headset 3 to anelectrical terminal of personal audio device 1. Personal audio device 1may provide a display to a user and receive user input using a touchscreen 2, or alternatively, a standard liquid crystal display (LCD) maybe combined with various buttons, sliders, and/or dials disposed on theface and/or sides of personal audio device 1. As also shown in FIG. 2,personal audio device 1 may include an audio integrated circuit (IC) 9for generating an analog audio signal for transmission to headset 3and/or another audio transducer.

FIG. 3 illustrates a block diagram of selected components of an exampleaudio IC 9 of a personal audio device, in accordance with embodiments ofthe present disclosure. As shown in FIG. 3, a microcontroller core 18may supply a digital audio input signal DIG_IN to a digital-to-analogconverter (DAC) 14, which may convert the digital audio input signal toan analog signal V_(IN). DAC 14 may supply analog signal V_(IN) to anamplifier 16 which may amplify or attenuate audio input signal V_(IN) toprovide a differential audio output signal V_(OUT), which may operate aspeaker, headphone transducer, a line level signal output, and/or othersuitable output. In some embodiments, DAC 14 may be an integralcomponent of amplifier 16. A power supply 10 may provide the powersupply rail inputs of amplifier 16. In some embodiments, power supply 10may comprise a battery. Although FIGS. 2 and 3 contemplate that audio IC9 resides in a personal audio device, systems and methods describedherein may also be applied to electrical and electronic systems anddevices other than a personal audio device, including audio systems foruse in a computing device larger than a personal audio device, anautomobile, a building, or other structure.

FIG. 4 illustrates a block and circuit diagram of selected components ofan example switched mode amplifier 20, in accordance with embodiments ofthe present disclosure. In some embodiments, switched mode amplifier 20may implement all or a portion of amplifier 16 described with respect toFIG. 3. As shown in FIG. 4, switched mode amplifier 20 may comprise amodulator 22, a converter controller 24, and a power converter 26.

Modulator 22 may comprise any system, device, or apparatus configured toreceive an input signal (e.g., audio input signal V_(IN) or a derivativethereof) and a feedback signal (e.g., audio output signal V_(OUT), aderivative thereof, or other signal indicative of audio output signalV_(OUT)) and based on such input signal and feedback signal, generate acontroller input signal to be communicated to converter controller 24.In some embodiments, such controller input signal may comprise a signalindicative of an integrated error between the input signal and thefeedback signal, as is described in greater detail below with referenceto FIGS. 6, 9 and 25. In other embodiments, such controller input signalmay comprise a signal indicative of a target current signal to be drivenas an output current I_(OUT) to a load coupled to the output terminalsof power converter 26, as described in greater detail below withreference to FIGS. 26 and 27.

Converter controller 24 may comprise any system, device, or apparatusconfigured to, based on the controller input signal, sequentially selectamong operational modes of power converter 26 and based on a selectedoperational mode, communicate a plurality of control signals to powerconverter 26 to apply a switch configuration from a plurality of switchconfigurations of switches of power converter 26 to selectively activateor deactivate each of the plurality of switches in order to transferelectrical energy from a power supply V_(SUPPLY) to the load ofswitched-mode amplifier 20 in accordance with the selected operationalmode. Examples of operational modes and switch configurations associatedwith each are described in greater detail elsewhere in this disclosure.Example implementations of converter controller 24 are also described ingreater detail elsewhere in this disclosure. In addition, in someembodiments, converter controller 24 may control switches of a powerconverter 26 in order to regulate a common mode voltage of the outputterminals of power converter 26 to the maximum of a first voltageassociated with switched-mode amplifier 20 and a second voltageassociated with switched-mode amplifier 20. In some embodiments, thefirst voltage may comprise one-half of the supply voltage V_(SUPPLY). Inthese and other embodiments, the second voltage may comprise one-half ofoutput voltage V_(OUT), or another signal indicative of an expectedvoltage for output voltage V_(OUT) (e.g., input voltage signal V_(IN)).

Power converter 26 may receive at its input a voltage V_(SUPPLY) (e.g.,provided by power supply 10) at its input, and may generate at itsoutput audio output signal V_(OUT). Although not explicitly shown inFIG. 3, in some embodiments, voltage V_(SUPPLY) may be received viainput terminals including a positive input terminal and a negative inputterminal which may be coupled to a ground voltage. As described ingreater detail in this disclosure, power converter 26 may comprise apower inductor and a plurality of switches that are controlled bycontrol signals received from converter controller 24 in order toconvert voltage V_(SUPPLY) to audio output signal V_(OUT), such thataudio output signal V_(OUT) is a function of the input signal tomodulator 22. Examples of power converter 26 each are described ingreater detail elsewhere in this disclosure.

FIG. 5 illustrates a circuit diagram of selected components of anexample power converter 26A, in accordance with embodiments of thepresent disclosure. In some embodiments, power converter 26A depicted inFIG. 5 may implement all or a portion of power converter 26 describedwith respect to FIG. 4. As shown in FIG. 5, power converter 26A mayreceive at its input a voltage V_(SUPPLY) (e.g., provided by powersupply 10) at input terminals, including a positive input terminal and anegative input terminal which may be coupled to a ground voltage, andmay generate at its output a differential output voltage V_(OUT). Powerconverter 26A may comprise a power inductor 42, and a plurality ofswitches 31, 33, 35, 37, 38, and 39. Power inductor 42 may comprise anypassive two-terminal electrical component which resists changes inelectrical current passing through it and such that when electricalcurrent flowing through it changes, a time-varying magnetic fieldinduces a voltage in power inductor 42, in accordance with Faraday's lawof electromagnetic induction, which opposes the change in current thatcreated the magnetic field.

Each switch 31, 33, 35, 37, 38, and 39 may comprise any suitable device,system, or apparatus for making a connection in an electric circuit whenthe switch is enabled (e.g., closed or on) and breaking the connectionwhen the switch is disabled (e.g., open or off) in response to a controlsignal received by the switch. For purposes of clarity and exposition,control signals for switches 31, 33, 35, 37, 38, and 39 (e.g., controlsignals communicated from converter controller 24) are not depictedalthough such control signals would be present to selectively enable anddisable switches 31, 33, 35, 37, 38, and 39. In some embodiments, aswitch 31, 33, 35, 37, 38, 39 may comprise an n-typemetal-oxide-semiconductor field-effect transistor. Switch 31 may becoupled between the positive input terminal and a first terminal ofpower inductor 42. Switch 33 may be coupled between a negative terminalof the output of power converter 26A and a second terminal of powerinductor 42. Switch 35 may be coupled between a positive terminal of theoutput of power converter 26A and the second terminal of power inductor42. Switch 37 may be coupled between the first terminal of powerinductor 42 and the ground voltage. Switch 38 may be coupled between thepositive terminal of the output of power converter 26A and the groundvoltage. Switch 39 may be coupled between the negative terminal of theoutput of power converter 26A and the ground voltage.

In addition to switches 31, 33, 35, 37, 38, 39 and power inductor 42,power converter 26A may include a first output capacitor 46 coupledbetween the negative terminal of the output of power converter 26A andthe ground voltage and a second output capacitor 48 coupled between thepositive terminal of the output of power converter 26A and the groundvoltage. Each output capacitor 46 and 48 may comprise a passivetwo-terminal electrical component used to store energy electrostaticallyin an electric field, and may generate a current in response to atime-varying voltage across the capacitor.

As described above, a power converter 26A may operate in a plurality ofdifferent operational modes, and may sequentially operate in a number ofswitch configurations under each operational mode. The plurality ofmodes may include, without limitation, a boost mode, a buck mode, and ahold mode.

FIG. 6 illustrates a table setting forth switch configurations of powerconverter 26A when operating in the boost mode, in accordance withembodiments of the present disclosure. In the boost mode, powerconverter 26A may act as a boost converter to boost the magnitude of theoutput voltage V_(OUT) above that of supply voltage V_(SUPPLY). Powerconverter 26A may operate in a boost mode, for example, when thecontroller input signal indicates that a magnitude of an integratederror between output voltage V_(OUT) and an input voltage signal tomodulator 22 is above a threshold (e.g. |V_(OUT)−V_(IN)|>1.5V). As shownin FIG. 6, when the integrated error is positive, and during a chargingphase T1 of power converter 26A, converter controller 24 may enableswitches 31, 33, and 39 of power converter 26A, with such switchconfiguration resulting in the equivalent circuit depicted in FIG. 7.When the integrated error is positive, and during a discharge phase T2of power converter 26A, converter controller 24 may enable switches 31,35, and 39 of power converter 26A, with such switch configurationresulting in the equivalent circuit depicted in FIG. 8. Similarly, whenthe integrated error is negative, and during a charging phase T1 ofpower converter 26A, converter controller 24 may enable switches 31, 35,and 38 of power converter 26A. In addition, when the integrated error isnegative, and during a discharge phase T2 of power converter 26A,converter controller 24 may enable switches 31, 33, and 38 of powerconverter 26A. Thus, in the boost mode, converter controller 24 maycontrol switches of power converter 26A to charge capacitor 46 orcapacitor 48 during the charging phase T1 and transfer charge to thesame capacitor 46 or capacitor 48 from the power supply (e.g., powersupply 10) during the discharge phase T2.

In some embodiments, when operating in the boost mode, convertercontroller 24 may operate to control switches of power converter 26A intwo or more sub-modes of the boost mode. For example, for largermagnitudes of an integrated error between output voltage V_(OUT) and aninput voltage signal to modulator 22 (e.g., |V_(OUT)−V_(IN)|>2.0V),converter controller 24 may cause power converter 26A to cyclicallyoperate in the charging phase T1 for one clock cycle and the dischargephase T2 for one clock cycle, to maximize the charge transferred to theoutput terminal of power converter 26A. On the other hand, for smallermagnitudes of an integrated error between output voltage V_(OUT) and aninput voltage signal to modulator 22 (e.g., 1.5V<|V_(OUT)−V_(IN)|<2.0V), converter controller 24 may cause powerconverter 26A to cyclically operate in the charging phase T1 for oneclock cycle and the discharge phase T2 for two clock cycles, to transfera smaller amount of charge to the output terminal of power converter 26Athan would occur if the discharge phase T2 was asserted for only asingle clock cycle.

FIG. 9 illustrates a table setting forth switch configurations of powerconverter 26A when operating in the buck mode, in accordance withembodiments of the present disclosure. In the buck mode, power converter26A may act as a buck converter to generate a magnitude of the outputvoltage V_(OUT) below that of supply voltage V_(SUPPLY). Power converter26A may operate in a buck mode, for example, when the controller inputsignal indicates that a magnitude of an integrated error between outputvoltage V_(OUT) and an input voltage signal to modulator 22 is below thethreshold for operating in the boost mode (e.g. |V_(OUT)−V_(IN)|<1.5V)but has a magnitude significantly above zero (e.g., e.g.|V_(OUT)−V_(IN)|>0.25V). As shown in FIG. 9, when the integrated erroris positive, and during a charging phase T1 of power converter 26A,converter controller 24 may enable switches 31, 33, and 39 of powerconverter 26A, with such switch configuration resulting in theequivalent circuit depicted in FIG. 10. When the integrated error ispositive, and during a discharge phase T2 of power converter 26A,converter controller 24 may enable switches 35, 37, and 39 of powerconverter 26A, with such switch configuration resulting in theequivalent circuit depicted in FIG. 11. Similarly, when the integratederror is negative, and during a charging phase T1 of power converter26A, converter controller 24 may enable switches 31, 35, and 38 of powerconverter 26A. In addition, when the integrated error is negative, andduring a discharge phase T2 of power converter 26A, converter controller24 may enable switches 33, 37, and 38 of power converter 26A. Thus, inthe buck mode, converter controller 24 may control switches of powerconverter 26A to charge capacitor 46 or capacitor 48 during the chargingphase T1 and transfer charge between capacitor 46 and capacitor 48during the discharge phase T2.

In some embodiments, when operating in the buck mode, convertercontroller 24 may operate to control switches of power converter 26A intwo or more sub-modes of the buck mode. For example, for largermagnitudes of an integrated error between output voltage V_(OUT) and aninput voltage signal to modulator 22 (e.g., 0.75<|V_(OUT)−V_(IN)|<1.5V),converter controller 24 may cause power converter 26A to cyclicallyoperate in the charging phase T1 for one clock cycle and the dischargephase T2 for one clock cycle, to maximize the charge transferred to theoutput terminal of power converter 26A. On the other hand, for smallermagnitudes of an integrated error between output voltage V_(OUT) and aninput voltage signal to modulator 22 (e.g., 0.25V<|V_(OUT)−V_(IN)|<0.75V), converter controller 24 may cause powerconverter 26A to cyclically operate in the charging phase T1 for oneclock cycle and the discharge phase T2 for two clock cycles, to transfera smaller amount of charge to the output terminal of power converter 26Athan would occur if the discharge phase T2 was asserted for only asingle clock cycle.

In some embodiments, in addition to a boost mode and a buck mode, powerconverter 26A may operate in a hold mode. The hold mode may occur, forexample, when the controller input signal indicates that a magnitude ofan integrated error between output voltage V_(OUT) and an input voltagesignal is near zero (e.g. |V_(OUT)−V_(IN)|<0.25V). During such hold modeneither of capacitors 46 and 48 may be charged nor discharged during acharging phase of power converter 26A and in which no charge istransferred to or from capacitors 46 and 48 during a discharge phase ofpower converter 26A.

In some embodiments, converter controller 24 may control switches ofpower converter 26A such that the switches perform synchronousrectification, wherein all switches of power converter 26A arecontrolled (e.g., disabled if inductor current I_(L) decrease to zero)in order to prevent inductor current I_(L) from decreasing below zero.In other embodiments, power converter 26A may include a diode (e.g.,with anode terminal coupled to power inductor 42 and cathode terminalcoupled to switches 33 and 35) in order to prevent inductor currentI_(L) from decreasing below zero.

FIG. 12 illustrates a circuit diagram of selected components of anexample power converter 26B, in accordance with embodiments of thepresent disclosure. In some embodiments, power converter 26B depicted inFIG. 12 may implement all or a portion of power converter 26 describedwith respect to FIG. 4. As shown in FIG. 12, power converter 26B mayreceive at its input a voltage V_(SUPPLY) (e.g., provided by powersupply 10) at input terminals, including a positive input terminal and anegative input terminal which may be coupled to a ground voltage, andmay generate at its output a differential output voltage V_(OUT). Powerconverter 26B may comprise a power inductor 62, a plurality of switches51-60, and a linear amplifier 70. Power inductor 62 may comprise anypassive two-terminal electrical component which resists changes inelectrical current passing through it and such that when electricalcurrent flowing through it changes, a time-varying magnetic fieldinduces a voltage in power inductor 62, in accordance with Faraday's lawof electromagnetic induction, which opposes the change in current thatcreated the magnetic field.

Each switch 51-60 may comprise any suitable device, system, or apparatusfor making a connection in an electric circuit when the switch isenabled (e.g., closed or on) and breaking the connection when the switchis disabled (e.g., open or off) in response to a control signal receivedby the switch. For purposes of clarity and exposition, control signalsfor switches 51-60 (e.g., control signals communicated from convertercontroller 24) are not depicted although such control signals would bepresent to selectively enable and disable switches 51-60. In someembodiments, a switch 51-60 may comprise an n-typemetal-oxide-semiconductor field-effect transistor. Switch 51 may becoupled between the positive input terminal and a first terminal ofpower inductor 62. Switch 52 may be coupled between a second terminal ofpower inductor 62 and ground. Switch 53 may be coupled between apositive terminal of the output of power converter 26B and a secondterminal of power inductor 62. Switch 54 may be coupled between anegative terminal of the output of power converter 26B and the firstterminal of power inductor 62. Switch 55 may be coupled between anegative terminal of the output of power converter 26B and the secondterminal of power inductor 62. Switch 56 may be coupled between apositive terminal of the output of power converter 26B and the firstterminal of power inductor 62. Switch 57 may be coupled between theground voltage and the first terminal of power inductor 62. Switch 58may be coupled between the negative terminal of the output of powerconverter 26B and the ground voltage. Switch 59 may be coupled betweenthe positive terminal of the output of power converter 26B and theground voltage. Switch 60 may be coupled between the positive inputterminal the second terminal of power inductor 62.

Power converter 26B may be similar in structure to power converter 26A,in that switches 31, 33, 35, 37, 38, and 39 of power converter 26A arearranged in a manner similar to switches 51, 53, 55, 57, 58, and 59,respectively, of power converter 26B. However, power converter 26Badditionally includes switches 52, 54, 56, and 60, which enables powerconverter 26B to operate in switch configurations of operational modesin which neither of the output terminals of power converter 26B arecoupled to the ground voltage, whereas in power converter 26A, eachswitch configuration includes one of the output terminals of powerconverter 26A coupled to the ground voltage. By including suchadditional switches enabling operational modes in which neither of theoutput terminals of power converter 26B is coupled to the groundvoltage, additional operational modes of power converter 26B may beprovided, as described in greater detail below.

In addition to switches 51-60 and power inductor 62, power converter 26Bmay include a first output capacitor 66 coupled between the positiveterminal of the output of power converter 26B and the ground voltage anda second output capacitor 68 coupled between the negative terminal ofthe output of power converter 26B and the ground voltage. Each outputcapacitor 66 and 68 may comprise a passive two-terminal electricalcomponent used to store energy electrostatically in an electric field,and may generate a current in response to a time-varying voltage acrossthe capacitor.

Linear amplifier 70, which is shown as a current source in FIG. 12, maycomprise any system, device, or apparatus configured to generate acurrent in response to an input signal. In some embodiments, linearamplifier 70 may comprise a digital-to-analog converter (DAC) configuredto convert a digital input signal (e.g., a digital signal indicative ofa desired output current across a load coupled between the outputterminals of power converter 26B) into an analog current. Functionalityof linear amplifier 70 is described in greater detail elsewhere in thisdisclosure.

As described above, a power converter 26B may operate in a plurality ofdifferent operational modes, and may sequentially operate in a number ofswitch configurations under each operational mode. The plurality ofmodes may include, without limitation, a single-ended boost mode, adifferential-output buck-boost mode, a differential-output buck mode,and a linear amplifier mode.

Power converter 26B may operate in a single-ended boost mode when outputvoltage V_(OUT) has a magnitude significantly larger than the supplyvoltage V_(SUPPLY) (e.g., |V_(OUT)|>V_(SUPPLY)=2V). FIG. 13 illustratesa table setting forth switch configurations of power converter 26B whenoperating in the single-ended boost mode, in accordance with embodimentsof the present disclosure. As shown in FIG. 13, when output voltageV_(OUT) is positive, and during a charging phase T1 of power converter26B, converter controller 24 may enable switches 51, 52, and 58 of powerconverter 26B, with such switch configuration resulting in theequivalent circuit depicted in FIG. 14. In such switch configuration,power inductor 62 may be charged via a current flowing between the powersupply (e.g., power supply 10) and ground. When output voltage V_(OUT)is positive, and during a discharge phase T2 of power converter 26B,converter controller 24 may enable switches 51, 53, and 58 of powerconverter 26B, with such switch configuration resulting in theequivalent circuit depicted in FIG. 15. In such switch configuration,power inductor 62 may be discharged, with charge transferred from thepower supply (e.g., power supply 10) to the positive terminal of theoutput of power converter 26B. Similarly, when output voltage V_(OUT) isnegative, and during the charging phase T1 of power converter 26B,converter controller 24 may enable switches 51, 52, and 59 of powerconverter 26B, wherein in accordance with such switch configuration,power inductor 62 may be charged via a current flowing between the powersupply (e.g., power supply 10) and ground. In addition, when outputvoltage V_(OUT) is negative, and during the discharge phase T2 of powerconverter 26B, converter controller 24 may enable switches 51, 55, and59 of power converter 26B, wherein in accordance with such switchconfiguration, power inductor 62 may be discharged, with chargetransferred from the power supply (e.g., power supply 10) to thenegative terminal of the output of power converter 26B.

Notably, in the boost configuration, one of either of the terminals ofthe output of power converter 26B remains grounded in order to providefor operation in the boost mode, thus allowing power converter 26B toact as a boost converter when in the boost mode.

In some embodiments, it may be desirable to operate in a continuouscurrent mode (CCM) as opposed to a discontinuous current mode (DCM) whenoperating power converter 26B in the single-ended boost mode. Thispreference is because a CCM boost converter may have lowerroot-means-square (e.g., ripple) currents compared to a correspondingDCM boost converter.

For an input voltage signal V_(I) to modulator 22, modulator 22 maygenerate a target current signal I_(TGT) as the controller input signalwhich may be given by I_(TGT)=V_(I)/R_(OUT), where R_(OUT) is animpedance of a load at the output of power converter 26B. A duration ofcharging phase T1 may be given by T1=(1−D)TT, where D is a unitlessvariable given by D=1−(V_(SUPPLY)/V_(I)) and TT is a switching period ofpower converter 26B which is the sum of the durations of the chargingphase T1 and the transfer phase T2 (e.g., TT=T1+T2). A change in powerinductor current I_(L) occurring during charging phase T1 may be givenby ΔI_(L)=T1×(V_(SUPPLY)/L) where L is an inductance of power inductor62. A minimum inductor current I_(min) may be given by:I _(min)=[2×TT×I _(TGT)×(V _(SUPPLY) −V _(I))/L−ΔI _(L) ² ]/ΔI _(L)and a peak current I_(pk) for inductor current IL may be given asI_(pk)=I_(min)+ΔI_(L).

Power converter 26B may operate in a differential-output buck-boost modewhen output voltage V_(OUT) has a magnitude lower than that for whichthe single-ended boost mode is appropriate (e.g.,|V_(OUT)|<V_(SUPPLY)+2V) but higher than a particular thresholdmagnitude (e.g., |V_(OUT)|>3V) for which the duration of a chargingphase T1 becomes too small to operate power converter 26B in abuck-boost mode. FIG. 16 illustrates a table setting forth switchconfigurations of power converter 26B when operating in thedifferential-output buck-boost mode, in accordance with embodiments ofthe present disclosure. As shown in FIG. 16, when output voltage V_(OUT)is positive, and during a charging phase T1 of power converter 26B,converter controller 24 may enable switches 51 and 52 of power converter26B, with such switch configuration resulting in the equivalent circuitdepicted in FIG. 17. In such switch configuration, power inductor 62 maybe charged via a current flowing between the power supply (e.g., powersupply 10) and ground. When output voltage V_(OUT) is positive, andduring a discharge phase T2 of power converter 26B, converter controller24 may enable switches 53 and 54 of power converter 26B, with suchswitch configuration resulting in the equivalent circuit depicted inFIG. 18. In such switch configuration, power inductor 62 may bedischarged, with charge transferred from the negative terminal of theoutput of power converter 26B to the positive terminal of the output ofpower converter 26B. Similarly, when output voltage V_(OUT) is negative,and during the charging phase T1 of power converter 26B, convertercontroller 24 may enable switches 51 and 52 of power converter 26B,wherein in accordance with such switch configuration, power inductor 62may be charged via a current flowing between the power supply (e.g.,power supply 10) and ground. In addition, when output voltage V_(OUT) isnegative, and during the discharge phase T2 of power converter 26B,converter controller 24 may enable switches 55 and 56 of power converter26B, wherein in accordance with such switch configuration, powerinductor 62 may be discharged, with charge transferred from the positiveterminal of the output of power converter 26B to the negative terminalof the output of power converter 26B.

Thus, in the differential-output buck-boost mode, power inductor 62 maybe charged from V_(SUPPLY) to ground during charging phases T1, and indischarging phases T2, power inductor 62 may be coupled across theoutput terminals of a load at the output of power converter 26 in orderto discharge power inductor 62 and create a differential output.Coupling power inductor 62 across the output terminals in a differentialoutput fashion may lead to a greater charge differential betweencapacitors 66 and 68 than would be in a single-ended configuration(e.g., with one of the output terminals grounded). Thus, lower powerinductor peak currents may be required to achieve the same outputcurrent.

Within the output voltage range of operation for the differential-outputbuck-boost mode, power converter 26B may operate in CCM for largeroutput voltages (e.g., 7V<V_(OUT)<V_(SUPPLY)+2V) and DCM for smalleroutput voltages (e.g., 3V<V_(OUT)<7V). In DCM, peak current I_(pk) ofpower inductor 62 may be given by:

$I_{p\; k} = \sqrt{\frac{2 \times I_{TGT} \times V_{OUT} \times {TT}}{L}}$where TT is a switching period of power converter 26.

In CCM, a duration of charging phase T1 may be given by T1=D×TT, where Dis a unitless variable given by D=V_(OUT)/(V_(OUT)+V_(SUPPLY)) and TT isa switching period of power converter 26B which is the sum of thedurations of the charging phase T1 and the transfer phase T2 (e.g.,TT=T1+T2). A change in power inductor current I_(L) occurring duringcharging phase T1 may be given by ΔI_(L)=T1×(V_(SUPPLY)/L). A minimuminductor current I_(min) may be given by:I _(min) =[I _(OUT) ×TT×V _(OUT) /L−ΔI _(L) ²/2]/ΔI _(L)and a peak current I_(pk) for inductor current I_(L) may be given asI_(pk)=I_(min)+ΔI_(L).

Power converter 26B may operate in a differential-output buck mode whenoutput voltage V_(OUT) has a magnitude lower than that for which theduration of a charging phase T1 becomes too small to operate powerconverter in a buck-boost mode (e.g., |V_(OUT)|<3V) and a magnitudehigher than for which the duration of a charging phase T1 becomes toosmall (e.g. |V_(OUT)|>1V) to operate power converter 26B in a buck mode.FIG. 19 illustrates a table setting forth switch configurations of powerconverter 26B when operating in the differential-output buck-boost mode,in accordance with embodiments of the present disclosure. As shown inFIG. 19, in the differential-output buck mode, switch configurations maynot only be based on the polarity of output voltage V_(OUT), but also onwhether the common-mode voltage of the positive output terminal and thenegative output terminal of power converter 26B is to be increased ordecreased to regulate the common-mode voltage at a desired level, asshown in the column with the heading “CM” in FIG. 19. For example, insome embodiments, converter controller 24 may control switches of powerconverter 26B in order to regulate the common mode to a voltageassociated with switched-mode amplifier 20. In some embodiments, thevoltage may comprise one-half of the supply voltage V_(SUPPLY).

As shown in FIG. 19, during a charging phase T1 of power converter 26B,when output voltage V_(OUT) is positive and the common-mode voltage ofthe output terminals is to be increased, converter controller 24 mayenable switches 51 and 53 of power converter 26B, with such switchconfiguration resulting in the equivalent circuit depicted in FIG. 20.In such switch configuration, power inductor 62 may be charged via acurrent flowing between the power supply (e.g., power supply 10) and thepositive terminal of the output of power converter 26B, thus generatinga positive output voltage V_(OUT) and increasing the common-mode voltageby increasing the electrical charge on capacitor 66. On the other hand,during a charging phase T1 of power converter 26B, when output voltageV_(OUT) is positive and the common-mode voltage of the output terminalsis to be decreased, converter controller 24 may enable switches 52 and54 of power converter 26B, with such switch configuration resulting inthe equivalent circuit depicted in FIG. 21. In such switchconfiguration, power inductor 62 may be charged via a current flowingbetween the negative terminal of the output of power converter 26B andground, thus generating a positive output voltage V_(OUT) and decreasingcommon-mode voltage by decreasing the electrical charge on capacitor 68.During a discharge phase T2 of power converter 26B, when target currentI_(TGT) is positive and regardless of whether the common-mode voltage ofthe output terminals is to be increased or decreased, convertercontroller 24 may enable switches 53 and 54 of power converter 26B, withsuch switch configuration resulting in the equivalent circuit depictedin FIG. 22. In such switch configuration, power inductor 62 may bedischarged, with charge transferred from the negative terminal of theoutput of power converter 26B to the positive terminal of the output ofpower converter 26B in order to provide a positive output voltageV_(OUT) while maintaining the same common-mode voltage.

Similarly, during a charging phase T1 of power converter 26B, whenoutput voltage V_(OUT) is negative and the common-mode voltage of theoutput terminals is to be increased, converter controller 24 may enableswitches 51 and 55 of power converter 26B. In such switch configuration,power inductor 62 may be charged via a current flowing between the powersupply (e.g., power supply 10) and the negative terminal of the outputof power converter 26B, thus generating a negative output voltageV_(OUT) and increasing the common-mode voltage by increasing theelectrical charge on capacitor 68. On the other hand, during a chargingphase T1 of power converter 26B, when output voltage V_(OUT) is negativeand the common-mode voltage of the output terminals is to be decreased,converter controller 24 may enable switches 52 and 56 of power converter26B. In such switch configuration, power inductor 62 may be charged viaa current flowing between the positive terminal of the output of powerconverter 26B and ground, thus generating a negative output voltageV_(OUT) and decreasing common-mode voltage by decreasing the electricalcharge on capacitor 66. During a discharge phase T2 of power converter26B, when output voltage V_(OUT) is negative and regardless of whetherthe common-mode voltage of the output terminals is to be increased ordecreased, converter controller 24 may enable switches 55 and 56 ofpower converter 26B. In such switch configuration, power inductor 62 maybe discharged, with charge transferred from the positive terminal of theoutput of power converter 26B to the negative terminal of the output ofpower converter 26B in order to provide a negative output voltageV_(OUT) while maintaining the same common-mode voltage.

Thus, during charging phases T1, converter controller 24 may cause powerconverter 26B to couple a capacitor 66 or 68 to supply voltageV_(SUPPLY) or ground to increase or decrease the total amount of chargein capacitors 66 and 68 in order to regulate common-mode voltage of theoutput terminals. On the other hand, discharge phases T2 of convertercontroller 24 may cause power converter 26B to couple a power inductor62 across the output terminals, which may redistribute charge betweencapacitors 66 and 68. Accordingly, in the differential-output buck mode,power converter 26B uses common-mode voltage at the output to createdifferential output voltage V_(OUT), as the duration of charging phaseT1 may determine the common mode voltage and differential voltageV_(OUT) while the duration of discharge phase T2 may additionallydetermine the differential voltage V_(OUT). As compared to other modesof operation, the differential-output buck mode provides for efficientcharge transfer as charge is pushed to an output capacitor 66 or 68during charging phase T1 and redistributed between output capacitors 66and 66 during discharge phase T2. Because of such charge-transferscheme, lower peak currents through power inductor 62 may be necessaryto transfer charge as compared to other modes. Also, root-mean-squarecurrent through switch 51 may be reduced as it is not exercised as muchas it is in other modes of operation, which may minimize powerdissipation of switch 51. Common-mode voltage at the output terminalsmay also be well-controlled, as common-mode control is achieved bycoupling an output capacitor 66 or 68 to supply voltage V_(SUPPLY) orground through power inductor 62.

When operating in the differential-output buck mode, power converter 26may typically operate in DCM, unless power inductor 62 has a very highinductance (e.g., greater than 500 nH). In DCM, peak current I_(pk) ofpower inductor 62 may be given by:

$I_{p\; k} = \sqrt{\frac{2 \times I_{TGT} \times V_{OUT} \times \left( {V_{SUPPLY} - V_{OUT}} \right) \times {TT}}{L \times V_{SUPPLY}}}$where TT is a switching period of power converter 26B.

In CCM, a duration of charging phase T1 may be given by T1=D×TT, where Dis a unitless variable given by D=V_(OUT)/(V_(OUT)+V_(SUPPLY)) and TT isa switching period of power converter 26B which is the sum of thedurations of the charging phase T1 and the transfer phase T2 (e.g.,TT=T1+T2). A change in power inductor current I_(L) occurring duringcharging phase T1 may be given by ΔI_(L)=T1×(V_(SUPPLY)−V_(OUT))/2L. Aminimum inductor current I_(min) may be given by:I _(min) =[I _(OUT) ×TT×(V _(SUPPLY) −V _(OUT))×TT/(L×V _(SUPPLY))−ΔI_(L) ²/2]/ΔI _(L)and a peak current I_(pk) for inductor current IL may be given asI_(pk)=I_(min)+ΔI_(L).

In some embodiments, converter controller 24 may control switches ofpower converter 26B such that the switches perform synchronousrectification, wherein all switches of power converter 26B arecontrolled (e.g., disabled if inductor current I_(L) decrease to zero)in order to prevent inductor current I_(L) from decreasing below zero.In other embodiments, power converter 26B may include a diode (e.g.,with anode terminal coupled to power inductor 62 and cathode terminalcoupled to switches 53 and 55) in order to prevent inductor currentI_(L) from decreasing below zero.

In addition to providing switch control signals to power converter 26B,converter controller 24 may also provide a digital linear amplifierinput signal to power converter 26 for controlling a current generatedby a linear amplifier internal to power converter 26B, as described ingreater detail below. As described above, power converter 26B mayoperate at magnitudes of output voltage V_(OUT) for which the durationof the charging phase T1 remains high enough (e.g. |V_(OUT)|>1V) tooperate power converter 26B in a buck mode. To provide for fineresolution of output voltages at magnitudes lower than the operationalrange of the differential-output buck mode, power converter 26B mayoperate in a linear DAC mode, in which linear amplifier 70 of FIG. 12,operating in effect as a DAC, may be used to convert a digital linearamplifier control signal (which may be indicative of a desired outputcurrent I_(OUT)) communicated from converter controller 24 into ananalog current driven to a load coupled between output terminals ofpower converter 26B.

FIG. 23 illustrates a circuit diagram of selected components of anotherexample power converter 26C, in accordance with embodiments of thepresent disclosure. Power converter 26C may, in some embodiments, beused as an alternative to power converter 26B, and may in many respects,be mathematically equivalent to power converter 26B and/or operate in asimilar manner to power converter 26B. As shown in FIG. 23, powerconverter 26C may receive at its input a voltage V_(SUPPLY) (e.g.,provided by power supply 10) at input terminals, including a positiveinput terminal and a negative input terminal which may be coupled to aground voltage, and may generate at its output a differential outputvoltage V_(OUT). Power converter 26C may comprise a power inductor 62A,and a plurality of switches 51A-58A. Although not shown in FIG. 23,power converter 26C may also include across its output terminals alinear amplifier identical or similar to linear amplifier 70 of poweramplifier 26B. Power inductor 62A may comprise any passive two-terminalelectrical component which resists changes in electrical current passingthrough it and such that when electrical current flowing through itchanges, a time-varying magnetic field induces a voltage in powerinductor 62A, in accordance with Faraday's law of electromagneticinduction, which opposes the change in current that created the magneticfield.

Each switch 51A-58A may comprise any suitable device, system, orapparatus for making a connection in an electric circuit when the switchis enabled (e.g., closed or on) and breaking the connection when theswitch is disabled (e.g., open or off) in response to a control signalreceived by the switch. For purposes of clarity and exposition, controlsignals for switches 51A-58A (e.g., control signals communicated fromconverter controller 24) are not depicted although such control signalswould be present to selectively enable and disable switches 51A-58A. Insome embodiments, a switch 51A-58A may comprise an n-typemetal-oxide-semiconductor field-effect transistor. Switch 51A may becoupled between the positive input terminal and a first terminal ofpower inductor 62A. Switch 52A may be coupled between the positive inputterminal and a second terminal of power inductor 62A. Switch 53A may becoupled between the first terminal of power inductor 62A and the groundvoltage. Switch 54A may be coupled between the second terminal of powerinductor 62A and the ground voltage. Switch 55A may be coupled betweenthe first terminal of power inductor 62A and a negative terminal of theoutput of power converter 26C. Switch 56A may be coupled between thesecond terminal of power inductor 62A and a positive terminal of theoutput of power converter 26C. Switch 57A may be coupled between thenegative terminal of the output of power converter 26C and the groundvoltage. Switch 58A may be coupled between the positive terminal of theoutput of power converter 26C and the ground voltage.

In addition to switches 51A-58B and power inductor 62A, power converter26C may include a first output capacitor 66A coupled between thepositive terminal of the output of power converter 26C and the groundvoltage and a second output capacitor 68A coupled between the negativeterminal of the output of power converter 26C and the ground voltage.Each output capacitor 66A and 68A may comprise a passive two-terminalelectrical component used to store energy electrostatically in anelectric field, and may generate a current in response to a time-varyingvoltage across the capacitor.

FIG. 24 illustrates a graph of an example output voltage V_(OUT) havinga sinusoidal waveform, the graph indicating example ranges for operationin the various operational modes of power converter 26B. Thus, for afull-scale sinusoidal signal, power converter 26B may sequentiallyoperate in the linear DAC mode, the differential-output buck mode, thedifferential output buck-boost mode, the single-ended boost mode, thedifferential output buck-boost mode, the differential-output buck mode,and the linear DAC mode for each half-cycle of output voltage V_(OUT).

FIG. 25 illustrates a block diagram of selected components of an examplemodulator 22A, in accordance with embodiments of the present disclosure.In some embodiments, modulator 22A depicted in FIG. 25 may implement allor a portion of modulator 22 described with respect to FIG. 4.

Modulator 22A may comprise any suitable system, device, or apparatusconfigured to generate an appropriate converter input signal such thatconverter controller 24 controls the plurality of switches of powerconverter 26 in order to generate a desired output voltage V_(OUT) inresponse to an input signal INPUT. Input signal INPUT may be anysuitable current, voltage, or power signal indicative of a targetvoltage to be generated as output voltage V_(OUT). In some embodiments,input signal INPUT may comprise analog signal V_(IN) or a derivativethereof. In other embodiments, input signal INPUT may comprise digitalaudio input signal DIG_IN or a derivative thereof, in which casemodulator 22A and/or its components may perform the functionality of DAC14. As shown in FIG. 25, modulator 22A may comprise a loop filter 72.Loop filter 72 may comprise any system, device, or apparatus configuredto generate an integrated error INT_ERROR between output voltage V_(OUT)and a target input voltage corresponding to input signal INPUT. In someembodiments, loop filter 72 may comprise a proportional-integral loopfilter. In these and other embodiments, loop filter 72 may comprise aquantizer 74 configured to quantize the integrated error INT_ERRORcalculated by loop filter 72 to one of a plurality of quantizationlevels. Such quantized integrated error may be communicated to convertercontroller 24, such that converter controller 24 may control switches ofpower converter 26 in accordance with a selected mode corresponding tosuch quantized integrated error. For example, in embodiments employingpower converter 26A, the plurality of quantization levels may comprise afirst quantization level for an integrated error less than −2.0 volts, asecond quantization level for an integrated error between −2.0 volts and−1.5 volts, a third quantization level for an integrated error between−1.5 volts and −0.75 volts, a fourth quantization level for anintegrated error between −0.75 volts and −0.25 volts, a fifthquantization level for an integrated error between −0.25 volts and 0.25volts, a sixth quantization level for an integrated error between 0.25volts and 0.75 volts, a seventh quantization level for an integratederror between 0.75 volts and 1.5 volts, an eighth quantization level foran integrated error between 1.5 volts and 2.0 volts, and a ninthquantization level for an integrated error greater than 2.0 volts. Insuch embodiments, the first quantization level and the ninthquantization level may correspond to a first sub-mode of the boost modeof power converter 26A, the second quantization level and the eightquantization level may correspond to a second sub-mode of the boost modeof power converter 26A, the third quantization level and the seventhquantization level may correspond to a first sub-mode of the buck modeof power converter 26A, the fourth quantization level and the sixthquantization level may correspond to a second sub-mode of the buck modeof power converter 26A, and the fifth quantization level may correspondto the hold mode. Notably, because the input signal INPUT may vary overtime, integrated error INT_ERROR may sequentially switch among thevarious quantization levels.

FIG. 26 illustrates a block diagram of selected components of an examplemodulator 22B, in accordance with embodiments of the present disclosure.In some embodiments, modulator 22B depicted in FIG. 26 may implement allor a portion of modulator 22 described with respect to FIG. 4.

Modulator 22B may comprise a delta-sigma modulator or similar modulatorwhich may have the function of moving quantization errors outside theaudio band. Modulator 22B may include a loop filter which comprises aninput summer 73 for generating a difference between an input signal(e.g., an analog voltage signal V_(IN)) and a feedback signal (e.g.,output voltage V_(OUT)), and one or more integrator stages 74, such thatthe loop filter operates as analog filter of an error signal equal tothe difference between the input signal and the feedback signal, andgenerates, at the output of output summer 75 a filtered analog signal toanalog-to-digital converter (ADC) 78 based on the input signal and thefeedback signal. The inputs to output summer 75 may include the inputsignal as modified by a feed-forward gain coefficient K_(F) applied by again element 76, the outputs of individual integrator stages 74 as eachis modified by a respective integrator gain coefficient K₁, K₂, . . . ,K_(N) applied by gain elements 76, and the output of a feedbackdigital-to-analog converter 80 as modified by a delay-compensationcoefficient K_(F) applied by a gain element 76 in order to compensatefor excess loop delay of the loop filter.

ADC 78 may comprise any system, device, or apparatus for converting theanalog output signal generated by the loop filter (e.g., the output ofoutput summer 75) into an equivalent digital signal, which, in someembodiments, may represent a desired output voltage to be generated atthe output of switched mode amplifier 20 (e.g., across the terminalslabeled V_(OUT) in FIG. 5). Such digital signal or a derivative thereof(e.g., a current signal based on the input signal) may be communicatedto converter controller 24, such that converter controller 24 maycontrol switches of power converter 26 in accordance with a selectedmode corresponding to such quantized integrated error.

DAC 80 may comprise any suitable system, device, or apparatus configuredto convert the digital signal into an equivalent analog feedback signal.

FIG. 27 illustrates a block diagram of selected components of an exampleconverter controller 24A, in accordance with embodiments of the presentdisclosure. In some embodiments, converter controller 24A depicted inFIG. 27 may implement all or a portion of converter controller 24described with respect to FIG. 4. In the embodiments represented by FIG.27 the controller input signal received by converter controller 24A is atarget current signal I_(TGT). As shown in FIG. 27, converter controller24A may implement an ADC 82, a mode determiner 84, a peak currentcomputation block 86, a DAC 88, a peak current detector 90, a clock 92,a phase determiner 94, and a switch controller 96.

ADC 82 may comprise any system, device, or apparatus configured toconvert analog output voltage V_(OUT) (or a derivative thereof) into anequivalent digital signal V_(OUT) _(_) _(DIG).

Mode determiner 84 may comprise any system, device, or apparatusconfigured to select a mode of operation from a plurality of modes ofoperation (e.g., single-ended boost mode, differential-output buck-boostmode, differential-output buck mode, linear DAC mode, etc.) based ondigital output voltage signal V_(OUT) _(_) _(DIG) (or another signalindicative of output voltage V_(OUT)) and/or a digital input voltagesignal V_(I) _(_) _(DIG) indicative of input voltage V_(IN). Forexample, mode determiner 82 may select the mode of operation based upona voltage range of digital output voltage signal V_(OUT) _(_) _(DIG)and/or digital input voltage signal V_(I) _(_) _(DIG) (e.g., selectsingle-ended boost mode for |V_(FB)|>14V), select differential-outputbuck-boost mode for 3V<|V_(FB)|<14V, select differential-output buckmode for 1V<|V_(FB)|<3V, and select linear DAC mode for |V_(I)|<1V.

Peak current computation block 86 may comprise any system, device, orapparatus configured to compute a peak current I_(pk) to be driventhrough power inductor 62 during a switching cycle of power converter26. Such peak current I_(pk) may be calculated based on the selectedmode of operation, digital output voltage signal V_(OUT) _(_) _(DIG) (oranother signal indicative of output voltage V_(OUT)), supply voltageV_(SUPPLY), output current I_(OUT) (or another signal indicative ofoutput current I_(OUT)), and/or target current I_(TGT) in accordancewith the various equations for peak current I_(pk) set forth above.

DAC 88 may comprise any system, device, or apparatus configured toconvert a digital signal generated by peak current computation block 106indicative of peak current I_(pk) into an equivalent analog peak currentsignal I_(pk).

Peak current detector 90 may comprise any system, device, or apparatusconfigured to compare power inductor current I_(L) to the analog peakcurrent signal I_(pk) and generate an output signal indicative of thecomparison, thus providing an indication for when power inductor currentI_(L) has reached its desired peak current. Power inductor current I_(L)has reaching its desired peak current may indicate the end of a chargingphase T1 and beginning of a transfer phase T2 of power converter 26.

Clock 92 may comprise any system, device, or apparatus configured togenerate a periodic timing signal indicative of an occurrence of orwithin a switching cycle of power converter 26. For example, a zerocrossing, edge, or other characteristic of a waveform generated by clock92 may indicate the beginning of a charging phase T1 of power converter26.

Phase determiner 94 may comprise any system, device, or apparatusconfigured to, based on the outputs of peak current detector 90 andclock 92, determine which phase (e.g., charging phase T1 or dischargephase T2) power converter 26 is to operate.

Switch controller 96 may comprise any system, device, or apparatusconfigured to, based on the mode of operation, phase, polarity ofdigital input signal V_(I) _(_) _(DIG) (or another signal indicative ofinput voltage V_(IN) or output voltage V_(OUT)), and (for thedifferential-output buck mode of power converter 26B) a common-modevoltage V_(CM) of the output terminals of power converter 26, generateswitch control signals for controlling the switches of power converter26.

Thus, during each switching cycle for converter controller 24A,converter controller 24A may select a mode of operation based on inputvoltage V_(IN) and output voltage V_(OUT), calculate a peak currentI_(pk) based on input voltage V_(IN), output voltage V_(OUT), targetcurrent signal I_(TGT), and/or output current I_(OUT), and useinformation regarding the selected mode and the phase of power converter26 to select a switch configuration to control the switches of powerconverter 26. In alternative embodiments, rather than operating as apeak current system as depicted in FIG. 27, converter controller 24 mayoperate as a time-based system based on measurements of supply voltageV_(SUPPLY), output voltage V_(OUT), and output current I_(OUT).

Thus, in the various embodiments disclosed herein, the choice ofsequence for switches of power converter 26 may be made consistent witha desired change in output voltage V_(OUT). By repeatedly increasing anddecreasing output voltage V_(OUT) in small steps, output voltage V_(OUT)may be made to follow, on average, the desired audio signal.Accordingly, quantization error present in output voltage V_(OUT) may bemoved outside the audio band in a manner similar to a delta-sigmamodulator.

As used herein, absolute voltage values (e.g., 0.25V, 0.75 V, 1.5V, 2.0Vfor power converter 26A; 1V, 3V, 7V, 14V for power converter 26B) aregiven merely as examples, and any other suitable voltages may be used todefine ranges of operation of the various power converter modesdescribed herein.

As used herein, when two or more elements are referred to as “coupled”to one another, such term indicates that such two or more elements arein electronic communication or mechanical communication, as applicable,whether connected indirectly or directly, with or without interveningelements.

This disclosure encompasses all changes, substitutions, variations,alterations, and modifications to the exemplary embodiments herein thata person having ordinary skill in the art would comprehend. Similarly,where appropriate, the appended claims encompass all changes,substitutions, variations, alterations, and modifications to theexemplary embodiments herein that a person having ordinary skill in theart would comprehend. Moreover, reference in the appended claims to anapparatus or system or a component of an apparatus or system beingadapted to, arranged to, capable of, configured to, enabled to, operableto, or operative to perform a particular function encompasses thatapparatus, system, or component, whether or not it or that particularfunction is activated, turned on, or unlocked, as long as thatapparatus, system, or component is so adapted, arranged, capable,configured, enabled, operable, or operative.

All examples and conditional language recited herein are intended forpedagogical objects to aid the reader in understanding the invention andthe concepts contributed by the inventor to furthering the art, and areconstrued as being without limitation to such specifically recitedexamples and conditions. Although embodiments of the present inventionshave been described in detail, it should be understood that variouschanges, substitutions, and alterations could be made hereto withoutdeparting from the spirit and scope of the disclosure.

What is claimed is:
 1. A switching power stage for producing an outputvoltage to a load, comprising: a power converter comprising a powerinductor and plurality of switches arranged to sequentially operate in aplurality of switch configurations; and a controller configured to:sequentially select selected operational modes of the power converterfrom a plurality of operational modes, the plurality of operationalmodes comprising at least a differential buck mode in which thecontroller sequentially applies the plurality of switch configurationsto selectively activate or deactivate each of the plurality of switchesin order to operate the power converter as a differential output buckconverter, such that: during a charging phase of the power converter,the power inductor is coupled between (i) one of a first terminal of apower source and a second terminal of the power source and (ii) one of afirst terminal of an output load and a second terminal of the outputload; during a transfer phase of the power converter, at least one ofthe plurality of switches is activated in order to couple the powerinductor between the first terminal of the output load and the secondterminal of the output load and decouple both of the first terminal ofthe output load and the second terminal of the output load from both ofthe first terminal of the power source and the second terminal of thepower source, such that during the transfer phase, an amount of chargeis transferred from one of the first terminal of the output load and thesecond terminal of the output load is substantially equal to an amountof charge transferred to the other of the first terminal of the outputload and the second terminal of the output load; and the output voltagecomprises a differential voltage between the first terminal and thesecond terminal; and for each particular mode of the plurality ofoperational modes, selectively activate or deactivate each of theplurality of switches so as to generate a current of the power inductorbased on an output signal of a modulator and the particular mode, inorder to, for each of the plurality of operational modes, cause thepower converter to convert the output signal of the modulator to theoutput voltage.
 2. The switching power stage of claim 1, wherein thecontroller is further configured to regulate a common mode voltage ofthe first terminal of the output load and the second terminal of theoutput load at a predetermined voltage.
 3. The switching power stage ofclaim 2, wherein the predetermined voltage is approximately equal toone-half of a source voltage provided by an input source.
 4. Theswitching power stage of claim 2, wherein: the first terminal of thepower source has a larger voltage potential than the second terminal ofthe power source; and the controller is configured to regulate thecommon mode voltage during the charging phase by: coupling the powerinductor between the first terminal of the power source and one of thefirst terminal of the output load and the second terminal of the outputload to increase the common mode voltage; and coupling the powerinductor between the second terminal of the power source and one of afirst terminal of the output load and a second terminal of the outputload to decrease the common mode voltage.
 5. The switching power stageof claim 1, wherein the load is an acoustic transducer.
 6. The switchingpower stage of claim 1, wherein the controller controls switching of theplurality of switches to produce the output voltage as a function of aninput signal.
 7. The switching power stage of claim 6, wherein the inputsignal is an audio signal.
 8. A method for producing an output voltageto a load, comprising: in a power converter comprising a power inductorand plurality of switches arranged to sequentially operate in aplurality of switch configurations, sequentially selecting selectedoperational modes of the power converter from a plurality of operationalmodes, the plurality of operational modes comprising at least adifferential buck mode wherein the plurality of switches sequentiallyapply a plurality of switch configurations to selectively activate ordeactivate each of the plurality of switches in order to operate thepower converter as a differential output buck converter, such that:during a charging phase of the power converter, the power inductor iscoupled between (i) one of a first terminal of a power source and asecond terminal of the power source and (ii) one of a first terminal ofan output load and a second terminal of the output load; during atransfer phase of the power converter, at least one of the plurality ofswitches is activated in order to couple the power inductor between thefirst terminal of the output load and the second terminal of the outputload and decouple both of the first terminal of the output load and thesecond terminal of the output load from both of the first terminal ofthe power source and the second terminal of the power source, such thatduring the transfer phase, an amount of charge is transferred from oneof the first terminal of the output load and the second terminal of theoutput load is substantially equal to an amount of charge transferred tothe other of the first terminal of the output load and the secondterminal of the output load; and the output voltage comprises adifferential voltage between the first terminal and the second terminal;and for each particular mode of the plurality of operational modes,selectively activating or deactivating each of the plurality of switchesso as to generate a current of a power inductor of the power converterbased on an output signal of a modulator and the particular mode, inorder to, for each of the plurality of operational modes, cause thepower converter to convert the output signal of the modulator to theoutput voltage.
 9. The method of claim 8, wherein the controller isfurther configured to regulate a common mode voltage of the firstterminal of the output load and the second terminal of the output loadat a predetermined voltage.
 10. The method of claim 9, wherein thepredetermined voltage is approximately equal to one-half of a sourcevoltage provided by the input source.
 11. The method of claim 9,wherein: the first terminal of the power source has a larger voltagepotential than the second terminal of the power source; and thecontroller is configured to regulate the common mode voltage during thecharging phase by: coupling the power inductor between the firstterminal of the power source and one of the first terminal of the outputload and the second terminal of the output load to increase the commonmode voltage; and coupling the power inductor between the secondterminal of the power source and one of a first terminal of the outputload and a second terminal of the output load to decrease the commonmode voltage.
 12. The method of claim 8, wherein the load is an acoustictransducer.
 13. The method of claim 8, wherein the controller controlsswitching of the plurality of switches to produce the output voltage asa function of an input signal.
 14. The method of claim 13, wherein theinput signal is an audio signal.